You want the Manual of Vascular Plants by Gleason and Cronquist (New York:
D. Van Nostrand Company, 1963, possibly subsequent eds.). Covers from the
Atlantic Ocean west to the western boundaries of Minnesota, Iowa, northern
Missouri and southern Illinois, south to the southern boundaries of
Virginia, Kentucky, and Illinois, and south to the Missouri River. Also
New Brunswick, Nova Scotia, PEI, and Ontario & Quebec south of the 47th
parallel.